[If you, like me, have been thinking about Lord of the Rings in some way every day for the majority of your life, please read!]

Point 8 is where I think he makes his most assailable argument. He acknowledges that the eagles are direct representatives of Manwe, but points out that they clearly aren't constrained by Manwe's laissez faire policy when it comes to Middle-earth post-Flight of the Noldor. He lists several examples of Third Age intervention on the part of the eagles. However, most if not all of those examples are much less direct that what he suggests be done with the ring. Most show the eagles saving a person or group of people. The two times they interfere more directly (at the Battle of Five Armies, and at the last battle at the Black Gate), it is never stated in the text to my satisfaction exactly what level of interference they gave.

I have always extrapolated that at the end of the Hobbit, they mostly used their air presence to dismay and distract the goblins while the dwarves and elves rallied (I think there may be mention of dislodging goblins from high places where they have seized a battlefield advantage.) This is relatively indirect and could easily fit under any mandate Manwe had issued regarding interference in the Third Age (perhaps only a couple of times, or only when absolutely vital). I will also note that many of the peripheral characterizations in the Hobbit don't fit into the canon of the Lord of the Rings as well as Tolkien would have liked, because the Hobbit was written for a different purpose and at a different time than much of his other work. I'm not sure that we can let the eagles' actions at the Battle of Five Armies stand as direct evidence as to what their actions could potentially have been vis a vis the Fellowship.

Secondly, at the end of Return of the King, I felt that a) the eagles were present mostly to defy the Nazgul, and b) that there was a sort of "all bets are off" feel -- any interdict could feasibly have no longer applied. That's flimsy; I prefer 'a' to 'b' but felt like mentioning both. In any case, once again they arrived as a character whose point of view we were following departed, and we have little textual evidence of what actually happened.

I would further posit that under the hypothesis that Manwe still directly controls the eagles to an extent, he has most likely issued orders to them to help in circumspect ways if at all -- and that if indeed there is a chance the ring can be destroyed in a way that doesn't (overtly) involve Manwe's emissaries in Middle-earth, then let it be done that way. Of the main characters, Gandalf and perhaps Galadriel would be most likely to assume/understand this.